Paper documents are often promptly discarded after being read. Although paper is relatively inexpensive, the quality of discarded paper documents is enormous and the disposal of these discarded paper documents raises significant cost and environmental issues. As a consequence, it would be desirable that paper documents can be reusable, to minimize cost and environmental issues.
Photochromic paper, also known as erasable paper, provides an imaging medium that can be reused many times to transiently store images and documents. For example, photochromic paper employs photochromic materials to provide an imaging medium for containing desired images. Typically, photochromic materials can undergo reversible or irreversible photoinduced color changes in the photochromic containing imaging layer.
In addition, the reversible photoinduced color changes enable image-writing and image-erasure of photochromic paper in sequence on the same paper. For example, an ultraviolet (UV) light source can be used for inducing image-writing, while a combination of heat and a visible light source can be used for inducing image-erasure. However, problems can exist in the erasure process. For example, a chemical formulation of the photochromic document in combination with the heat and the visible light can fail to erase an image on the document to an acceptable shade or, upon conversion to a digital image, bit depth value. Further, the chemical formulation in combination with the heat and visible light can fail to erase the entire image on the document, resulting in portions or lines of unerased content. In these situations, the document is unacceptable on which to subsequently print.
A need, therefore, exists for systems and methods to ensure the erasure of a document. Further, a need exists for systems and methods to ensure that a document has been sufficiently erased to an acceptable level to be reused for printing purposes.